Friday Harbor Labs (FHL) scientists are helping a team of international investigators on the trail of several new harmful algal species in Puget Sound. Because Washington State shellfish growers sell over $77 million of product per year, this project is important in the preservation of Washington’s position as the leading producer of bivalves in the United States.

Several algal toxins are present in Puget Sound shellfish, making vigilant monitoring an essential component of ensuring the safety of shellfish consumers. The Washington State Department of Health (WDOH) analyzes thousands of shellfish samples per year for algal toxins.

However, in the summer of 2011 the first documented cases of diarrhetic shellfish poisoning (DSP) occurred when three people became ill after eating recreationally-harvested mussels collected from a dock in northern Puget Sound. This established the need to monitor for diarrhetic shellfish toxins in Puget Sound, which in 2012 were added to the suite of toxins monitored by the WDOH.

These DSP toxins are part of a larger group of lipophilic toxins including azaspiracids, which are monitored in the European Union. Due to the concern that other toxins from the lipophilic group might be present in local shellfish, a collaborative project was initiated between the FHL, NOAA’s Northwest Fisheries Science Center (NWFSC), the United States Food and Drug Administration (US FDA), the Alfred Wegener Institute in Germany, and the SoundToxins partnership (www.soundtoxins.org) to assess the risk of azaspiracids and azaspiracid shellfish poisoning (AZP) to shellfish safety in Puget Sound.

Beginning in 2014, Solid Phase Absorption Toxin Tracking (SPATT, Figure 1) disks were hung from docks at many sites around Puget Sound through the SoundToxins partnership (www.soundtoxins.org), including the Friday Harbor Labs in collaboration with Sandy Wyllie-Echeverria and volunteers in his lab. During the week-long deployment of SPATT disks in the water, dissolved toxins attach to the material contained in the disks. Extraction of SPATT resin in methanol and analysis by liquid chromatography mass spectroscopy has allowed us to assess the types and concentrations of azaspiracids in Puget Sound. To date, the azaspiracids that are monitored in Europe have not been detected. However, a new toxin named azaspiracid-59 (AZA-59) has been discovered in both SPATT and in shellfish. That said, concentrations of AZA-59 in Puget Sound shellfish are well below the European Union’s regulatory threshold.

At the same sites where SPATT disks were deployed, seawater samples were analyzed to detect the presence of two toxin producing species, Azadinium spinosum (Figure 2) and Azadinium poporum (a producer of AZA-59) as well as a non-toxic species, Azadinium obesum.

All three species were detected at several sites throughout Puget Sound over the past four summers (2014-2017). Sites where molecular probes detected the three Azadinium species in summer 2014 are shown in Figure 3. Azadinium species were detected at the Friday Harbor Labs dock during each summer.

Absence/presence map Fig. 3: Presence/absence of three Azadinium species in 2014.

Although Azadinium species as well as azaspiracid-59 are present at several sites in the Puget Sound region, the concentrations of both cells and toxins are well below the regulatory safety threshold for human consumption. However, our team is developing tools that can be used in refining the monitoring programs (for both the organisms and the toxins) that will used to proactively prevent future toxic events by promoting shellfish safety while protecting human health.